Kimberly-Clark publication WO-96/35018 describes the formation of patterns in a paper or tissue sheet using additional structures on the surface of a woven fabric. The imprint in this case is caused by providing systematically distributed areas of restricted drainage in the fabric. As disclosed in the publication, the drainage may be impeded by incorporation of additional filaments or fibers on top of or within the forming fabric weave pattern, or by a film or coating which blocks or fills void space within the fabric through which water could otherwise drain. Over the areas of impeded drainage, a thinner layer of relatively long fibers tends to be deposited, whilst shorter fibers migrate and are concentrated in the areas of more rapid drainage producing a thicker, less translucent tissue over the faster drainage areas.
Gusums Bruk AB Swedish Patent 427,053 discloses a forming fabric structure wherein areas of different density are created by providing relatively dense areas wherein there is a high frequency of yarn interweavings, and relatively porous regions wherein there is a low frequency of yarn interweavings, which are dominated by weft floats. In certain disclosed embodiments the areas of low frequency interweavings provide physically raised areas that shape the tissue.
Chiu U.S. Pat. No. 5,429,686 discloses a TAD fabric with a distinct load-bearing woven fabric layer and an additional sculpture layer formed by additional long-floated machine direction yarns, with the floats standing proud of the main body of the load-bearing fabric layer to shape the formed sheet.